OBJECTIVES: 1) Plasma membranes from rat pancreas will be radiolabeled with (32P)NAD in the presence of cholera toxin, preactivated with fluoride, GTP gamma S or CCK-8, then solubilized and cross-linked, and the radiolabeled species will be analyzed by PAGE and HPLC. 2) The kinetic parameters of two rat pancreatic calmodulin-stimulated cyclic nucleotide phsophodiesterases (isolated on calmodulin -Sepharose) will be examined. 3) Specific receptors for CCK will be examined in rat pancreatic plasma membranes and brain synaptosomal membranes and binding properties will be compared with the CCK-8 dependent GTPase activity of the same membranes. 4) The degradation of CCK-8 by aminopeptidase(s) and other proteases in pancreatic plasma membranes, brain synaptosomal membranes, and blood will be compared by HPLC. The biosynthesis of CCK-8 will be examined in vivo in gut. The sulfotransferase activity allowing the sulfatation of the tyrosine residue in CCK-8 will be tested in gut and brain. 5) Specific receptors for VIP will be further compared in pancreas, liver, lung and heart. The turnover of these receptors will be tested in hypo- and hyperthyroidism. 6) High- and low-affinity muscarinic receptors will be tested in rat pancreatic plasma membranes in the absence and presence of guanine nucleotides.